Source: Worldwatch Institute. Data updated with the BP Statistical Review
of World Energy.World Annual Oil Production (1900-2013) and Peak Oil (2010 Scenario)The oldest continuously operated oil well, called McClintock #1,
is located south of Titusville, Pennsylvania and started operations
in 1861. Its initial output was about 50 barrels of oil per day and
after more than 145 years of operation the well produces about 1 barrel
per day. This historical example indicates a process where an initially
abundant resource slowly gets depleted. Although the well is likely
to produce oil for a long time, it is beyond its peak production level.
Based upon this observation about a single well, it is possible to
infer that it applies to whole oil fields, and ultimately to global
oil production.The geophysicist King Hubbert published in 1956 a theory
concerning oil production, which takes the shape of a bell curve. Oil
production starts at zero and then rises to a peak which can never be
surpassed. Once peak production has been reached, production declines
and prices go up until oil resources are depleted or too costly to have
a widespread use. Hubbert predicted that oil production in the United
States would peak between 1965 and 1970, which attracted strong criticism,
even ridicule, from the oil industry. His assumption turned out to be
true and oil production in the United States peaked in 1971. Consequently,
his theory can be inferred to global oil reserves, but with much
uncertainty. The time framework for
which oil production is expected to peak is subject to much debate with
the International Energy Agency stating that peak oil would not occur
until around 2030. The only fundamental way to establish a peak oil
point is when the event has occurred. For the states of
Pennsylvania, Oklahoma and Texas, it was 1891, 1927 and 1972
respectively.Total oil reserves are estimated to be around 1,800 to 2,200 billion
barrels, with about 1,600 billion
barrels considered proven reserves. World annual consumption is
above 30 billion barrels per year. Under such circumstances, most of the
remaining oil could be extracted by 2060. However, several nuances have
to be brought forward:

New reserves. No large scale new oil reserves have
been found since the 1970s, which may lessen the oil reserves
that could be added to the 1,000 billion barrels of proven
reserves. There has been serious issues concerning the real
availability of oil reserves, as some figures have been inflated
to uphold the confidence of markets and investors. Since
reserves in many countries, mainly OPEC countries, are not audited
by external sources, reporting agencies are likely to have overestimated
potential oil reserves. Still, with technological development and
investments new reserves can be brought online, as the example
of tar sands and shale oil underline, but their economic
recoverability tend to involve much higher prices.

Demand. The consumption of oil is far from being a constant
growth process. Between 1990 and 2000, annual oil consumption increased
by 14% with expectations that this process may go on up to 2020,
especially in Pacific Asia with countries such as China importing
more oil, which explains the surge in global oil production that
took place after 2000.
Consequently, if demand goes up, the time remaining before the exhaustion
of global oil supplies could get shorter. Still, demand can also
decline for several reasons, namely with technological
improvements, shifts to alternative sources of energy, as well as with cycles of economic recession
where global and sectorial demand can face serious setbacks.

Recoverability. An historical perspective on the exploitation
of resources reveals that resources that are the easiest to access
are exploited first, while resources that are more difficult to
access are left for later times (if not overlooked). Oil extraction
has followed the same principle as most of the easy access oil has
now been extracted and what remains is located in more remote areas
(subarctic; offshore), is much deeper of is much more complex to
extract (e.g. tar sands and shale oil). This implies that the
oil that can be extracted is much more difficult to recover than
the oil that has been extracted so far. The last few hundred billion
barrels of oil may be economically unrecoverable.